DE69220263T2 - Method and apparatus for machine workpiece machining using a solid model algorithm - Google Patents

Description

Field of the invention.

The present invention relates to software methods for automatically generating numerical control (NC) tool paths in a CAD/CAM or manufacturing environment.

Background of the invention.

Mechanical CAD/CAM systems have existed for more than 20 years and became very popular in the late 1970s. Initially, CAD/CAM systems were used to create detailed designs of mechanical workpieces and to document designs using information such as dimensions and features. CAD/CAM systems increasingly extended to other applications such as analysis (e.g., finite element modeling) and manufacturing (e.g., generating NC toolpaths).

When workpieces are designed using a CAD/CAM system, the system creates computer models of those workpieces. To date, wire-frame and surface modeling have been the dominant representation schemes for CAD/CAM workpiece models. Wire-frame modeling models a workpiece by describing its edges (for example, a box is represented by 12 lines), and surface modeling models a workpiece by describing its faces (for example, a box is represented by 6 flat faces). However, these modeling technologies lack information describing how edges and faces are assembled to form the physical workpiece. They also lack information describing the inside and outside of the modeled workpiece. Due to these limitations, Wireframe and surface modeling technologies are classified as informally incomplete modeling representations. CAD/CAM applications based on these technologies cannot support full automation.

Once a workpiece is designed on a CAD/CAM system, NC toolpaths can be generated to automatically machine the workpiece. NC toolpaths are programs that control the operation of the machining tool as the machining tool cuts the workpiece from the stock or semi-finished product. A computer-aided design (CAD) system is used to create, document and analyze workpiece models, while a computer-aided manufacturing (CAM) system is used to generate NC toolpaths directly from the designed model. This approach has been only somewhat successful. Although a user (manufacturing engineer) of a CAM application may have a very well-defined strategy regarding how a workpiece is to be manufactured, today's CAD/CAM systems cannot support automatic NC toolpath calculation. The reason for this is that wire frame and surface models do not provide complete workpiece model information necessary for automated manufacturing.

For example, a user may need to create a toolpath for cutting a single-piece surface (for example, the inner bottom surface of a coffee mug). Creating a surface toolpath requires that x, y, z points, which are the programming points for the tool while the tool remains tangent to the surface of the entire surface, be calculated with a predetermined tolerance. When the resulting surface toolpath is performed on the machining tool, the lower Center of the cutting tool is moved to each of the predetermined x, y, z points of the tool path. The result of this is that the material in the path of the tool is removed.

Since surfaces are part of today's CAD/CAM modeling technologies, procedures exist for calculating NC toolpaths for the surface of a workpiece. However, knowledge of the surface of a workpiece alone is not sufficient. The cutting tool must not encroach on other surfaces of the workpiece model (for example, the sides of the coffee mug). This can happen because a cutting tool has a radius greater than zero. Therefore, if the cutting tool comes within a machining radius of an adjacent surface, additional material can be cut off from the adjacent surface. The machining tool cannot automatically avoid encroaching on adjacent surfaces because wire-frame and surface models lack a description of the relationships between the surfaces. For example, wire-frame and surface models do not describe that the bottom surface of the coffee mug is adjacent to the sides - the surfaces of the workpiece are modeled independently of each other.

The traditional way of solving this problem requires operator intervention. The operator must manually enter additional information before a workpiece can be produced. This is now done in a variety of convenient ways. All of them are time-consuming and prone to errors.

The most common way of doing CAM today is to create new surfaces specifically for machining. That is, instead of giving the system To "teach" that the sides of a coffee mug are adjacent to the bottom surface, the user creates a new bottom surface that is smaller (at least by the cutter radius) than the originally designed bottom surface. Consequently, the toolpaths created to machine the new bottom surface keep the cutter away from the adjacent surfaces.

This approach creates several problems. The most obvious is that the actual design model is not used for manufacturing, but a manufacturing model must be regenerated from the design model. This creates a gap between design and manufacturing, as the same model is not involved in both design and manufacturing. A second problem is that of time (productivity) and the potential for human error, as new surfaces must be created for each surface to be machined - potentially hundreds of surfaces for a single workpiece. Finally, the new surfaces are created based on the size of the cutting tool. If a different cutting strategy is desired, an entirely new set of surfaces must be generated for the manufacturing model.

Researchers developed a new modeling technology in the 1970s, called solid modeling, which became commercially available in the early 1980s, to overcome the limitations of wire-frame and surface modeling technologies. Solid modeling provides an informally complete representation of three-dimensional workpieces. While wire-frame and surface models only contain descriptions of the geometry of a workpiece to be manufactured, solid models have descriptions of the geometry and topology of the workpiece. The geometry of the workpiece is comparable to the geometry in wire-frame and surface modeling, but the topology of the workpiece is a "road map" that describes how surfaces defined by the model are fitted together to form the actual workpiece being modeled.

Since a volume model describes workpieces completely and unambiguously, higher-level operations, such as merging, differentiating or separating and intersecting workpiece models, are possible. For example, to create a hole in a workpiece, a volume model of a cylinder can be positioned on a volume model of a workpiece and geometrically subtracted - leaving the desired hole. Mathematically, this is a Boolean or logical operation. Logical operations are used throughout the invention described here.

Summary of the invention.

The present invention is a complete method and apparatus for manufacturing a workpiece using solid models and logical operations to generate NC toolpaths. The present invention uses solid models of the difference between the stock model and the workpiece model, the "delta volume," to calculate toolpaths for machining tools. Machining volumes are then created from the toolpaths. The machining volumes are then subtracted from the delta volume to obtain new delta volumes. This method automates the modeling of subsequent tool operations on a stock to produce a workpiece as designed.

The volume models are created using attributes such as semi-finished product, workpiece and delta volume. classified. Attributes can also be added to surfaces, holes, edges, vertices and features. The solid models and the attributes associated with the models, surfaces, features, etc. are used to determine the successive depths of cut for the machining operation. The user enters a machining setting and a machining strategy. The system automatically determines the best depths of cut from the solid models and the machining strategy. Each depth of cut is used to create a cutting plane which is superimposed on the surfaces of the solid modeling to determine the curves representing the areas into which the tool can enter. The solid model and the associated attributes are therefore used to prevent the tool from penetrating or damaging the workpiece.

An overview of the solid modeling process for manufacturing workpieces is graphically shown in Fig. 1. A solid model of the workpiece is first created in a block 20. The solid model contains a description of the surface geometry of the workpiece, the topology of the workpiece, and additional information describing features of the workpiece such as holes, projections, and depressions. The solid models can be created from a starting point, by reusing a previously created model from a computer library of solid models, or by modifying models obtained from the computer library. An example of a design model is shown in Fig. 2. Figures 2 through 8 are representations of images available from CRT displays of computer models.

Workpiece models are usually created in a design department using a CAD/CAM design struction system. These CAD/CAM systems support the creation of solid models that use a variety of modeling technologies that include the creation of primitive shapes such as blocks and cylinders, drawing closed 2-D profiles, and circular sweeps of 2-D profiles. The logical operations of union and discrimination are used throughout the design procedure. During each operation, the solid modeler maintains computer models that describe the topology and geometry of the resulting solid object.

Special features, such as holes, pockets, ridges or depressions, are inserted into the model of the workpiece. For example, a simple hole can be modeled by subtracting a cylinder from a model of the workpiece, leaving an inner cylindrical surface on the model. Information in the form of attributes can then be added to the cylindrical surface to describe the desired design, such as "for #2 Phillips screw". Machining cycles and tolerances to create a hole for a "# 2 Phillips screw" can then be derived.

Fig. 2 shows a computer model of a workpiece 201 as displayed on a CRT screen. The workpiece 201 is characterized, for example, by cylindrical holes 202, pockets 203, an outer surface 204, an inner pocket surface 205, and a transition surface 206. A transition surface is a surface that describes the transition from one surface to its adjacent surfaces such that the paths from the first surface to the second surface are continuous.

A schedule (block 21 in Fig. 1) is used to plan and document the stages of the machining process. The schedule is usually created early in the manufacturing cycle by a manufacturing engineer. The schedule may be in the form of a "macro," for example, heat treating the workpiece, machining the workpiece using machining tool #12 with the stock from bin #2, deburring the workpiece at machining center #15, and sending the finished workpiece for inspection. The schedule may include other specific details such as face milling the stock to a depth of 0.15; roughing the pockets to 0.50 and finish milling; spot drilling all holes and drilling 0.234" diameter holes. Schedules may range from fully documented schedules to schedules that exist only in the user's memory.

Three additional models are required to define the manufacturing process. These models are: 1) a stock model representing the exact shape of the blank that will be machined on the machining tool; 2) delta volumes representing volumes of material that will be machined during the manufacture of the workpiece; and 3) machining setup models including the machining table, fixtures, and clamps. These resulting models (block 23 in Fig. 1) are used throughout the machining process. The delta volume models are continuously updated throughout the manufacturing process. Stock models could be created interactively, but they are usually retrieved from existing stock shape databases. Machining setup models are also often retrieved from existing databases. Fig. 3 shows an example of a stock model 301 as displayed on a CRT screen. Fig. 3 also shows clamps 302 and Set-up knobs or stops 303. The clamps 302 hold the semi-finished product 301 on the machining table. The stops are used to precisely position the semi-finished product for machining. Delta volumes are automatically created using a logical solid modeling operation by subtracting the workpiece model from the semi-finished product model. The flow chart can further divide the delta volumes into smaller, more machineable delta volumes. From Fig. 4 it can be seen how the workpiece can be realized from the semi-finished product by positioning a solid model of the workpiece 201 within the solid model of the semi-finished product 301. Finally, by subtracting the workpiece from the semi-finished product, delta volumes are defined as shown in Fig. 5. In Fig. 5, the delta volume 501 is the volume of the semi-finished product 301 that does not remain on the workpiece 201. The delta volumes 502 are cylinders that represent the material to be removed to form the holes 202. The delta volumes 503 represent the material to be removed to create the pockets 203. The workpiece is created by machining the delta volumes, ie, the workpiece is created by programming the machining tool to remove the material defined by the delta volume(s).

Thus, the user can add simple and/or complex manufacturing attributes as he or she steps through the flow chart in block 10 of Figure 1. Simple attributes, such as the material type or surface finish for a face, are usually associated with the stock model. Complex attributes, such as a set of rules for machining a particular feature, such as a pocket or slot, are associated with that feature. An example of a complex attribute would be a machine strategy for a pocket, such as: (1) Initial hole with tool # 1; (2) Roughing the pocket with tool #2; (3) Finishing the bottom of the pocket with tool #3; (4) Finishing the side walls of the pocket with tool #4.

Next, the machining tool for producing the workpiece is selected, as well as the individual settings on the machine (semi-finished product positioning, fixtures, clamping, etc.), as shown by block 11 in Fig. 1. In this block, solid models of the machining table, fixtures attached to the machining table, and clamps for holding the semi-finished product to the fixtures are modeled. Like the semi-finished product models, the fixture and clamp models are usually selected from a library of predefined components. Any models not initially in the library are created as the need for these models increases. The fixtures and clamps are positioned in an overarching fashion, that is, the operator positions the fixture and clamp models by moving their graphical representations on a computer-controlled CRT screen using rotation and translation devices to obtain the correct location and orientation of each fixture or clamp. The output of a machining setup specification is the definition of the machining environment in block 22, complete with the orientations of the fixture and clamps. Block 11 marks the beginning of a repeating sequence of blocks 11 to 15, which is repeated until all delta volumes have been machined. On subsequent iterations, a new setup may or may not be required. According to Fig. 3, the machining environment includes stops to assist in positioning the semi-finished product and clamps to To keep the semi-finished product in place on the processing table.

Once a setup has been defined, the individual operations within the basic setup are planned and executed. The specification of the manufacturing operations according to block 12 begins with the selection of one or more delta volumes according to block 23 to be machined. The user then selects a machining strategy and a cutting tool to perform the operation according to block 24. The output in block 12 is the current delta volume and the machining strategy according to block 25 to remove the delta volume.

Block 13 represents the automatic generation of NC toolpaths. The inputs to block 13 contain the current delta volume to be machined from block 25, the associated machining strategy from block 25 and the definition of the machining environment according to block 22. NC machining paths are automatically generated in block 26 and saved for later machining with the actual machining tool. The NC toolpath generation can include automatic roughing, automatic finishing or a combination of both, as specified by the user.

The toolpaths are checked or confirmed in block 14. Here, machining volumes are automatically generated to model the total volume of the gap traversed by the cutting tool in the NC toolpath obtained from block 26. The machining volumes are then subtracted from the current delta volumes obtained from block 28 to model any material that was not removed. Material not removed becomes new delta volumes, which in turn stored and machined during subsequent machining steps as shown in block 23. The machining volumes are also subtracted from the stock model obtained by block 23 to model the exact shape of the stock after the current operation has been performed with the machining tool. The modified stock model becomes the current stock model and is stored in block 23. Fig. 6 shows two machining volumes 601 resulting from automatic toolpath generation of the pockets in the center of the workpiece. The machining volumes extend above the stock because they were modeled for the entire cylindrical length of the tool. When the machining volumes are subtracted from the delta volumes, Fig. 7 shows the result of the machining operation. Most of the pocket delta volumes have been removed, but some material remains around the walls of the pockets and in the corners of the pockets. This material is modeled as a new delta volume which will subsequently be machined with a different machining strategy.

This sequence continues until all delta volumes have been machined (block 15), whereupon all important machining data are collected in block 26 and processed for application to a numerically controlled machining tool, which is represented by block 27. Fig. 8 shows the example part 201 crystallized from the semi-finished product 301 after various machining operations have been performed. The volume 801 represents the volume of the semi-finished product 301 that was not actually removed by the tool cutting edge. The gap 802 represents material that was removed by the tool cutting edge. To separate the rest of the material, another machining setting is required, which must be specified again in block 11. so that the material under the clamps can be removed.

Overall, the present invention represents a significant advance in computer-aided manufacturing because, unlike conventional systems, it provides manufacturing engineers with an intuitive and powerful means for developing a strategy for machining a computer-modeled workpiece and specifying the strategy from which NC toolpaths are automatically generated. The present invention also provides manufacturing engineers with an intuitive means for performing planning, organizing, and communicating for the manufacture of workpieces using automatic toolpath generation. This process can achieve a significant increase in productivity over conventional computer-aided manufacturing.

A first purpose of the present invention is to provide methods for merging machining strategies and machining attributes of models of the workpiece to be manufactured and models of the semi-finished product of the workpiece to be manufactured.

A second purpose of the present invention is to provide methods for modeling the complete processing environment.

A third purpose of the present invention is to provide methods for modeling the exact amount of material to be removed (delta volume).

A fourth purpose of the present invention is to provide methods for associated processing strategies of the material to be removed (delta volume).

A fifth purpose of the present invention is to provide methods for automatically generating roughing toolpaths for delta volumes.

A sixth purpose of the present invention is to provide a method for automatically generating finishing toolpaths for all or portions of the delta volumes.

A seventh purpose of the present invention is to provide a method for modeling the material remaining after the machining operation for separation.

These and other aspects of the present invention are explained in more detail below in a detailed description of the invention by means of the accompanying figures and the associated claims.

Short description of the characters.

Fig. 1 is a flow chart for the entire software flow;

Fig. 2 is an example of a workpiece model obtained by the design;

Fig. 3 is an example of a semi-finished product model from which the workpiece is to be separated;

Fig. 4 is an example of a workpiece model positioned within a semi-finished product model;

Fig. 5 is an example of delta volumes obtained by subtracting the workpiece from the stock;

Fig. 6 is an example of machining volumes for two inner pockets of the workpiece;

Fig. 7 is an example of a modified delta volume and a modified semi-finished product;

Fig. 8 is an example of a semi-finished product after various passes through the process;

Fig. 9 is a flow chart describing the detailed process flow;

Fig. 10 is an example list describing a processing strategy;

Fig. 11 is a block diagram showing an automated ND roughing and finishing in detail;

Fig. 12 is a block diagram describing the detailed addition of the manufacturing attributes;

Fig. 13 is a block diagram describing the detailed modeling of the machining setting.

Detailed description of the invention.

The volume-based machining process is explained in detail with reference to Fig. 9. The procedure discussed here is based on certain basic characteristics of a volume modeler. The volume modeler must be reliable in performing logical operations, particularly with regard to the tangency and coplanarity of surfaces, as is known in the field. The procedure assumes a volume modeler that is exact (not approximate) and that has a boundary representation. The modeler must support the creation of the user's attributes on the model bodies, faces, edges, vertices and features. In addition, the modeler must allow the insertion of attributes during logical operations. One modeler suitable for this procedure is the ACIS Geometric Modeler from SPATIAL TECHNOLOGY INC., Boulder, Colorado, which is commercially available. Other solid modelers suitable for carrying out the present invention are the Parasolid modeler, available from McDonnell Douglas Corp., Cypress, California; XOX, available from XOX, Minneapolis, Minnesota; and Designbase, available from Ricoh Corp., Japan.

ACIS is written in C++. Certain embodiments of the present invention are described as employing ACIS. However, the present invention may be practiced with any of the solid modelers listed above, including all of the specific embodiments described herein.

A preferred embodiment of the present invention is shown in Fig. 9. The individual blocks according to Fig. 1 are represented by different sub-blocks in the representation of the present embodiment in Fig. 9, e.g. block 10 of Fig. 1 is represented by blocks 10-1, 10-2 and 10-3 in Fig. 9. Similarly, block 25 according to Fig. 1 is represented by blocks 25-1 and 25-2 in Fig. 9. Further details of the sequence according to the representation in Fig. 9 are shown in Fig. 10 (listing an example list describing a machining strategy for blocks 12-2 of Fig. 9); Fig. 11 (detailing the NC tool path generation, block 13 in Fig. 9); Fig. 12 (listing the sub-steps following block 10-1 in Fig. 9); and Fig. 13 (listing the sub-steps following the Block 11 in Fig. 9 follows. The steps of the preferred embodiment are described below. Each model created during this process carries with it an attribute which specifies whether that particular model is a model of, for example, workpiece models with an attribute which identifies the model as a model of a workpiece, and delta volume models with an attribute which identifies the model as a model of a delta volume.

STEP 1: CREATING THE SOLID MODEL OF THE WORKPIECE. As shown in block 20 in Fig. 9, the process begins with describing a solid model of the mechanical workpiece to be machined. The model can be created starting from a zero point, by reproducing a previously stored model, or by modifying a previously stored model. The model of the workpiece carries with it an attribute which identifies that the specific model is a model of a workpiece.

STEP 2: DEVELOP A PROCESS PLAN FOR MACHINING THE WORKPIECE The following step is to develop a process plan (block 21) for machining the workpiece. This step can be performed before or after steps 3, 4, 5, or 6. The process plan is the overall conceptual plan that describes how the workpiece is to be manufactured. It is performed in conjunction with steps 3, 4, 5, or 6, and not independently of them, i.e., the process plan can be adjusted based on the information developed in steps 3, 4, 5, or 6. For example, difficulties in developing a machining strategy in step 3 for a particular feature may require modifying the process plan to eliminate the source of the difficulty.

The flowchart guides the user's actions through the process. For example, the flowchart may require that the stock material be Aluminum #1. The user would make this specification by entering "Aluminum #1" as the material property attribute of the stock model. If the flowchart requires a tolerance of 0.0001 for selected holes, the user would enter "0.0001" as the hole diameter tolerance attribute for all selected holes.

STEP 3: ADDING MANUFACTURING ATTRIBUTES TO THE WORKPIECE. Manufacturing attributes can be added to the entire workpiece model, as well as to features, faces, edges, etc. of the workpiece (10-1). Techniques for adding attributes to solid models are well known in the field of solid modeling. They usually include input to additional data fields associated with the body of a workpiece, each face of the body, each edge of the body, and each vertex or transition point of the body. For example, all faces of the workpiece model are marked with a simple attribute that identifies each face as a bounding "part."

Manufacturing attributes can range from simple to complex. An example of a simple attribute is a real number attached to a face of a workpiece that identifies the thickness of material remaining on the face after the roughing toolpath is completed. A complex attribute could be a complete machining strategy for a feature. For example, a machining strategy for a pocket feature could be to initially drill the pocket, rough the pocket, finish the side walls of the pocket, and finish the bottom of the pocket. These and other attributes are used during the generation of the NC tool path (block 13) to provide appropriate tool control, as explained below with reference to Fig. 11.

There are a variety of ways to model complex attributes. The embodiment described here uses a text field attribute that contains an external file name. The external file contains information (a macro) that controls the machining operations during each machining step. This may include selecting one or more cutting tools, selecting the machining method, and modeling intermediate delta volumes through each machining step for the pocket.

The flow for adding machining attributes (block 10-1) is shown in more detail in Fig. 12. The flow begins by adding simple attributes to the part model that identify each of its faces as a bounding "part" (block 10-1a). Subsequently, face thickness attributes are added to each face (block 10-1b) as determined from the flow chart (block 21 in Fig. 9). Other simple or complex attributes may be added as necessary for generating the toolpath (block 10-1e).

STEP 4: CREATE THE SOLID MODEL OF THE SEMI-FINISHED PRODUCT. The user then creates a solid model of the semi-finished product (block 23-1) from which the workpiece is cut. Steps 3 and 4 must be performed before step 5, but can be performed in any order. The semi-finished product model can be created interactively or can already exist and be selected from a library of semi-finished product models. Semi-finished product attributes are added in the same way as workpiece attributes or manufacturing attributes. Attributes added at this time include attributes that identify the stock model as a "stock" (block 10-1c) and "air" attributes that identify the stock model surfaces that touch or are outside the air (block 10-1d). The "air" attribute may contain a numeric value that indicates how far the tool is allowed to move out of the stock and into the air. Stock attributes also contain material attributes that define the material of the stock with the type of material. The material type is used during NC toolpath generation to select, for example, the depth of cut, the machining tool, the tool step-over, the cutting pattern or shape, the overlap distance, the cutting direction, the type of cut (conventional or ramped), and the cutting tool requirements. The surfaces of the semi-finished product model can also be marked as limiting "air" so that optimal tool control can be achieved during the generation of the NC tool path (block 13 in Fig. 9).

STEP 5: SUBTRACTION OF WORKPIECE FROM SEMI-FINISHED PRODUCT. Once the workpiece model and the semi-finished product model are defined, the total material to be machined is determined by subtracting the workpiece model from the semi-finished product model (block 10-2). This material volume is represented as one or more volume models called delta volumes (block 23-2). During this logical operation, machining attributes picked up from the workpiece and semi-finished product models are migrated to corresponding surfaces of the delta volume(s), i.e., the relevant attributes of the workpiece and semi-finished product are automatically attached to new surfaces created by the logical operation. This allows, for example, sampling of "partial" surfaces (those of the workpiece model) on the delta volume. The attribute recording is carried out automatically by the solid modeling system.

STEP 6: SUBDIVISION OF DELTA VOLUMES. The user can then subdivide delta volumes into smaller delta volumes (block 10-3) as required by the flow chart in block 21. This can also be done such that individual delta volumes confirm the user's processing strategy. For example, an upper rectangular section of a delta volume can be subdivided into a separate delta volume which can be processed by "surface processing". The subdivision of delta volumes is performed, for example, interactively or by an expert system using volume modeling subdivision operations which create two or more new volume models (i.e., the delta volumes).

When a delta volume is subdivided, new surfaces are created on the models. During the subdivision of the delta volume, a "delta volume" attribute is added to re-create surfaces so that the surfaces can be identified as bordering another delta volume (not "air" or "work"). An attribute is also named to identify the other delta volume whose new surface is adjacent. This information can be used later during NC toolpath generation to determine where the cutting tool can and cannot move. After the delta volume subdivision process is complete, the total volume of material to be removed is presented as a list of delta volumes as shown in block 23-2.

STEP 7: MODEL MACHINING SETTING. The user models a machining setting in Block 11 to support one or more machining operations. The machining settings are used to align the workpiece, fixtures, and clamps on the machine tool. The settings are represented as solid models of clamps, fixtures, work tables, etc., and they are obtained as solid models called the current machining environment in block 22. The user selects the machining tool. Once the machining tool is selected, the user can access libraries of tools and fixtures that work with the selected machining tool. Machining limits, such as horizontal and vertical travel limits, are identified. The user interactively selects, positions, and checks the fixtures, clamps, stops, and other components of the machining environment by creating models of these components and positioning them on the CRT screen. The user can also design specific fixtures and clamps (see blocks 23-4 and 23-5 in Fig. 13).

The fixtures, clamps, and stock are selected according to the schedule using the manipulation functions of the solid modeler as shown in block 11-1 in Fig. 13. An "avoid" attribute is attached to the clamps and fixtures, making them prohibited locations for the tool upon entry during step 10 (block 11-2). A face thickness attribute may be added to the faces of the clamps and fixtures in block 11-3 to keep the tool spaced a safe distance from the clamps and fixtures.

The position and orientation of the models representing the machining environment define the volumes into which the tool is not allowed to enter. The attribute "Avoid" is added to each face to identify it as a fixture or clamp. This machining environment is used by the NC toolpath generation algorithm in block 13 to avoid generating tool motion that may interfere with machining components, as described below with reference to Fig. 11.

STEP 8: SELECTING A DELTA VOLUME FOR EDIT. The user then selects a delta volume for processing from the list of remaining delta volumes stored in block 23-2, as per block 12-1. The selected delta volume becomes the "current delta volume" and is stored in block 25-2.

STEP 9: SPECIFY THE MACHINING STRATEGY. The user then specifies a machining strategy in block 12-2. Machining strategies can be defined interactively or selected from a library of existing machining procedures in block 24. A machining strategy is specified and stored in a machining strategy file as per block 25-1, with parameters describing the tool selection and the type of tool entries and exits to be performed, the type of cut shape, the maximum depth of cut, how to control the coolant, etc., as dictated by the user's experience and expertise. An example machining procedure file is shown in Fig. 10.

STEP 10: NC TOOL PATH GENERATION. The current delta volume according to block 25-2, the current machining strategy according to block 25-1 and the current machining environment according to block 22 are then fed into the Block 13 and stored in Block 26. The generated NC toolpaths operate entirely through a delta volume, removing as much material as possible given the circumstances of the machining environment and the machining strategy used. The complete model information is used for all cuts to determine not only where the cutting tool can and cannot move, but also to determine the optimal machining tool feed based on how much material the tool is wrapping at any given time.

NC toolpath generation contains two main sections, automated roughing and automated finishing.

Automated roughing and finishing involves picking up a series of two-dimensional ("2-D") planar slices across an offset delta volume. The slices are determined perpendicular to the tool feed direction and result in one or more 2-D profiles (these are 2-D because Z remains constant across the profile). The profiles are then passed to the NC algorithm to generate roughing or finishing toolpaths. During roughing, the resulting profiles are "area cleaned" and during finishing, the resulting profiles represent the finishing toolpath.

The toolpath generation, block 13 in Fig. 9, is shown schematically in Fig. 11. It contains the following sub-steps:

Substep 10-1. Enter the current status.

The toolpath generation begins with block 13-10, in which the current delta volume, the current machining environment and the current strategy are entered The current delta volume is described in Fig. 9. The current machining environment is represented by zero or more solid models representing fixtures, clamps, the machining table, etc. Solid models containing the current environment have been assigned attributes that classify each model as a volume to "avoid" (this attribute assignment was performed in block 11 in Fig. 9). The current machining strategy contains the current tool and the current machining method. This strategy is represented by a list of variable assignments. A detailed example is given in Fig. 10. Most of the variables used in the machining strategy are standard controls used in classic CAD/CAM surface and wire frame machining systems. Those specific to solid-based machining are explained below.

Substep 10-2. Determine the maximum and minimum Z coordinates.

The maximum and minimum Z coordinate values (Z axis aligned with the tool axis direction) for the current delta volume are then determined (block 13-11). These Z extents are needed to determine the start and stop positions for cutting and steering (blocks 13-14 through 13-21 in Fig. 11). The Z extents for a delta volume are maintained and supplied by the underlying solid modeling system.

Sub-step 10-3. Checking critical flat surfaces.

All flat surfaces of the delta volume that are perpendicular to the tool feed direction are then checked (block 13-12) to see if a "critical" attribute has been assigned. Critical surfaces that, for example, have to be machined within a certain tolerance range were identified in step 10-1 in Fig. 9 with a FACE_THICKNESS attribute. Optionally, all planar surfaces of the workpiece with a face perpendicular to the tool feed direction can be designated as critical faces. Such faces must face the tool and lie within a user-specified tolerance in the perpendicular direction. Critical planar faces are designated with a value equal to the Z coordinate of the face (Z axis in the direction of the tool axis) plus the FACE_THICKNESS. These faces are organized in a list, sorted from maximum to minimum Z, and used in the subsequent substep 10-6.

Substep 10-4. Specify 2-D boundary profiles.

The user may optionally specify one or more 2-D boundary profiles (block 13-13) to further control where the cutting tool can and cannot move. A boundary profile is used internally in the algorithm to create a volume. This is accomplished by protruding the boundary profile through the Z extent of the delta volume (determined in sub-step 10-2). Boundary volumes nested with the delta volume define the volume in which the tool must reside. In this embodiment of the algorithm, boundary profiles are identified by the user using standard interactive technologies.

Substep 10-5. Repeat to remove the entire delta volume.

The following substeps 10-6 to 10-13 are repeated until the entire delta volume has been processed, i.e., until the CURRENT DEPTH (CURRENT_DEPTH) is below the minimum Z coordinate determined in substep 10-2.

Substep 10-6. Determination of Z depth.

The Z depth at which the next machining operation for the delta volume is determined as follows. A variable CURRENT DEPTH (initialized by Z_MAX in sub-step 10-2) defines the location of the previous machining pass. The variable NEXT_DEPTH is set to "CURRENT DEPTH + DEPTH OF CUT", where DEPTH_OF_CUT represents the maximum step in the Z direction (part of the current machining strategy). All critical surfaces identified in sub-step 10-3 are then checked to see if there are any required cuts between the CURRENT DEPTH and the NEXT DEPTH. If a critical surface is found, the NEXT DEPTH is set to the surface depth with the largest Z value between the CURRENT DEPTH and the NEXT DEPTH.

Substep 10-7. Creating an infinite plane (Blocks 13-15).

An infinite plane is then created (blocks 13-15) and positioned at the "NEXT DEPTH + TOOL RADIUS" with a normal plane aligned to the tool axis. The TOOL RADIUS is part of the machining strategy. This plane is used as the cutting plane in the following step of the algorithm.

Substep 10-8. Determine the tool center curves for each surface (blocks 13-16).

The tool center curve for each face is determined. Each face of the delta volume is offset by a value equal to "TOOL RADIUS + SURFACE THICKNESS" (block 13-16a). The SURFACE THICKNESS is a user attribute that defines the maximum amount of material remaining on the face after completion of this machining step. Techniques for offset faces are well known in surface modeling.

Each offset face is then subdivided (cut) in the plane defined in substep 10-7 (block 13-15) to yield a set of curves (block 13-16b). The curves are directed such that material is not allowed on the left side when looking in the direction of the curve. The resulting curves project over to the NEXT_DEPTH and are offset by the TOOL-FLAT (from the current tool description) to yield a set of curves (13-16c). These curves represent the locations of the tool tip tangent to the offset faces. Algorithms for projecting and offset curves in three dimensions are well known in surface modeling.

Substep 10-9. Determine the tool center curves for each edge (blocks 13-17).

The tool center curves for edges are then determined. For each edge of the delta volume, a transition surface is defined with a radius of curve equal to the tool radius plus the surface thickness between the offset surfaces (block 13-17a) connecting the edge in question. The calculation of a transition surface between two surfaces (cut surfaces) is well known in the field of surface modeling. The resulting transition surfaces are subdivided (cut) with a cutting plane to obtain a set of curves (block 13-17b). The curves are projected to the NEXT DEPTH and then offset by the TOOL FLAT (current tool) to obtain a set of curves (block 13-17c). These curves represent the tool tip tangent locations of the offset edges.

Substep 10-10. Determine the tool center curves for each vertex.

The tool center curves for vertices are then determined (Block 13- 18). For each transition point of the delta volume, a transition surface is defined between the offset surfaces (block 13-18a) that splits the transition point under consideration. The resulting transition surfaces are nested with the cutting plane to obtain a set of curves (block 13-18b). The curves are raised to the NEXT DEPTH and then offset by the TOOL-FLAT (current tool) to obtain a set of curves (block 13-18c). These curves represent the location of the tangent of the tool tip of the offset transition points.

Substep 10-11. Calculate the outline edges.

The contour edges (sometimes called view edge curves) are used to detect and avoid undercuts. The contour edges are calculated (block 13-19) for each of the offset faces, edges, and transition or vertex faces created in substeps 10-8 through 10-10 as described above. The view direction used to calculate the contour edges is from the Z direction (viewing orientation of the delta volume's cutting tool step). All contour edges that lie above the current cutting plane are raised (13-19b) to the current Z depth (NEXT DEPTH + TOOL RADIUS). The contour edge calculation is well known in the field of solid modeling.

Substep 10-12. Organizing the curves into profiles.

All necessary curves have been determined and the task now is to organize the curves into profiles. The algorithm is comparable to a 2-D logic operation. First, all curves calculated in substeps 10-8 to 10-11 are subdivided to obtain and store their intersection points (block 13-20a). The intersection points represent the locations where the curves change from an admissible to an inadmissible region. For example, if the curves calculated in substeps 10-8 through 10-11 are in the form of two intersecting pairs of parallel lines enclosing a feasible region in the shape of a square, then the procedure must find the intersection points at the four corners of the square. Each curve would then be divided into three segments. The segments outside the intersection points are discarded, leaving only the four curve segments that define the boundaries of the square. Therefore, decisions about whether to discard the curve segments are made at the intersection points.

Each curve at an intersection point is split into an input segment and an output segment and connected to the intersection point. The input and output segments are determined by considering the direction of the original (unsplit) curve, with the condition that it is not allowed to place the cutting tool to the left of a directed curve.

Substep 10-13. Define prohibited areas.

At each intersection point, each segment of the curve that enters and exits defines an area that is not allowed for the cutting tool. The cutting tool cannot enter these inadmissible areas without damaging the workpiece. By convention, the inadmissible area is placed on the left side of the curve segment (as viewed in the direction of the curve).

All intersection points are then considered in an arbitrary or user-defined sequence. The necessary steps to determine the prohibited areas around each individual point are now described. All curve segments participating in a transition point are this point is ordered (13-20b), using curvature to order the curve segments with equal entry angles. Entry/exit curve pairs determine regions that are acceptable for tool entry. For a selected curve segment, repeated counterclockwise inspection around the intersection point finds an entry curve immediately followed by an exit curve. Starting from this exit curve "A", repeated counterclockwise inspection through all exit curves is performed until an entry curve "B" is found. All exit curves between "A" and "B" are eliminated. Repeating clockwise from the original entry curve to eliminate all entry curves until an exit curve is found is similarly performed. The result is a single entry/exit curve pair for an intersection point, considering the path taken by the tool as it passes through this point. Eliminate the identified entry/exit curve pair and repeat the process until all entry/exit curve pairs for the intersection point have been identified. Each entry/exit curve pair must be compared to the workpiece volume, limit volume and avoidance volume derived from the models of the stock part, clamps and fixtures and machining environment. An entry/exit pair is eliminated if it lies within any of these disallowed regions.

After machining all intersection points, all paired entry/exit curves are connected to obtain a sequence of closed paths corresponding to the tool cycle around the workpiece (at a given Z level). These are the boundary curves (toolpath profiles). During automated roughing, the toolpath profile is area cleaned, and during automated finishing, the toolpath profile represents the final toolpath for the current level.

STEP 11: CREATE THE MACHINING VOLUME. The next step in the process, as shown in Fig. 9, is to create a machining volume (14-1) from the NC toolpath stored in block 26. A machining volume (23-3) is an exact solid model that represents the total volume of the space to be cut by the cutting tool during the complete traversal of the NC toolpath.

The machining volume is then subtracted from the delta volume (14-2). When subtracting the machining volume (with the cutting tool moving in clearance during the cut) from the delta volume, either the entire delta volume disappears or a portion of the delta volume remains. Portions of the remaining delta volume that are completely severed from the workpiece are not further machined, such as delta volume 801 in Fig. 8. If the delta volume adjacent to the workpiece disappears, the NC toolpath was successful in machining all of the material. If a portion of the delta volume remains adjacent to the workpiece, the NC toolpath was unable to remove all of the material. Each remaining delta volume is added to a list of delta volumes that remain to be machined (block 23-2). These delta volumes may be machined by a smaller tool.

STEP 12: MODELING THE INCREASE CHANGES IN THE SEMI-FINISHED PRODUCT. The machining volume is used to model the increase changes that the semi-finished product undergoes. This is achieved by geometrically subtracting the machining volume from the semi-finished product (23-1). The resulting semi-finished product model (23-1) can be used as visual documentation for flow charts and for a modification of the algorithm and/or an analysis.

STEP 13: END? When all delta volumes have been removed (15), the flow is finished. If more delta volumes remain for further processing, the flow is restarted with STEP 7, i.e., block 11 in Fig. 9. The flow can also end with some delta volumes remaining unremoved, for example because the user has decided to do so or because the unremoved delta volumes cannot be processed. The decision to leave some delta volumes unremoved is made in the flow plan (step 2 above).

Below is a summary of all essential features which, either alone or in combination with one another, define preferred embodiments of the present invention:

For a process for producing a workpiece, the following steps are important:

(1) Creating a computer model of the workpiece using a solid modeler;

(2) Creating a computer model of a semi-finished product using the solid modeler;

(3) Drawing up a process plan for the production of the workpiece;

(4) Linking the manufacturing attributes to the model of the workpiece;

(5) Determining at least one delta volume to be removed from the semi-finished part by subtracting the model of the workpiece from the model of the semi-finished part, and taking the manufacturing attributes from Model of the workpiece to a corresponding area of the at least one delta volume;

(6) Creating a model of a manufacturing setting;

(7) Creating a processing strategy;

(8) calculating tool paths for a numerically controlled manufacturing facility from the at least one delta volume according to the machining strategy and the manufacturing setup model;

(9) Calculating at least one machining volume, which represents the total volume of the space to be removed by the cutting tool;

(10) subtracting the at least one processing volume from the at least one delta volume to obtain a new delta volume;

(11) subtracting the at least one machining volume from the model of the semi-finished part to thereby model the machining of the tool paths and to verify that the tool paths have not damaged the workpiece;

(12) repeating steps (7) to (11) until the removal of the at least one delta volume has been modelled; and

(13) Manufacturing the workpiece according to the flow chart by transferring the tool paths to the numerically controlled machining tool, wherein steps 1 to 7 may generally be carried out in any order, provided that step (1) must precede step (4), steps (1) and (2) must precede step (5), and steps (1) to (7) must precede step (8).

- The machining strategy is achieved by retrieving data stored in a data storage device.

- The processing strategy is achieved by applying an expert system.

- The machining strategy is obtained from the data entered by a user.

- The manufacturing setup model is achieved by retrieving data stored in data storage devices.

- The production setting model is achieved by application of an expert system.

- The manufacturing setup model is achieved by data entered by a user.

The following features are important for the method of modeling successive machining operations that are carried out on a semi-finished part to produce a workpiece:

(1) Creating at least one feature volume, which is to be removed from the semi-finished part to create the workpiece;

(2) Creating a machining strategy;

(3) determining an initial tool path for at least one machining tool from the at least one feature volume and the machining strategy;

(4) Determining an initial machining volume from the initial tool path;

(5) performing a logical operation to subtract the initial machining volume from the feature volume to obtain a delta volume;

(6) Repeat step (3) with the delta volume to obtain a next tool path, step (4) to obtain a next machining volume from the next tool path, and step (5) to obtain a next delta volume; and

(7) Repeat step (6) until all delta volumes have been processed.

- The step of sequentially applying the initial toolpath and each subsequent toolpath to control a machining tool for removing the delta volume and each subsequent delta volume from the stock part.

- The feature volume is obtained by retrieving feature data stored in a data storage device.

- The feature volume is achieved by applying an expert system.

- The machining strategy is achieved by retrieving data stored in a data storage device.

- The processing strategy is achieved by applying an expert system.

- The machining strategy is obtained from data entered by a user.

- The step of determining an optimal feed rate for the initial and each subsequent tool path.

- The optimal feed rate is continuously variable according to the initial and each subsequent tool path.

- Manufacturing attributes for the feature volume are obtained by retrieving manufacturing data stored in a data storage device, the manufacturing attributes including data used in step (3) in determining the initial tool path and in step (6) in determining the next tool path.

- The machining strategy contains the manufacturing attributes.

- The step of sequentially applying the initial toolpath and each next toolpath to control at least one machining tool for removing the delta volume and each next delta volume from the semi-finished part, wherein the manufacturing attributes further include data used in selecting the at least one machining tool.

- The step of controlling the at least one machining tool at an optimal feed rate according to the initial and each subsequent tool path.

- The optimal feed rate is continuously variable according to the initial and each subsequent tool path.

- The tool path determined by the manufacturing attributes also contains specification data for the types of machining tool entry and exit, types of cutting shapes, maximum depth of cut and coolant control.

- The feature volume further contains a plurality of sub-feature volumes, wherein steps (3) to (7) is applied sequentially to each of the sub-feature volumes.

- The majority of sub-feature volumes are obtained from the feature volume by applying an expert system.

- The step of sequentially applying the initial toolpath and each next toolpath to control a machining tool to remove the delta volume and each next delta volume from the stock part for each of the plurality of sub-feature volumes.

- The sequence in which the sub-feature volumes are removed from the semi-finished part is determined by applying an expert system.

- A plurality of the sub-feature volumes are each dependent on a plurality of desired planar surfaces of the workpiece to be manufactured, the surfaces lying in parallel planes, and further comprising the step of removing these sub-feature volumes in a sequence determined by their relative clearance in a direction perpendicular to these planar surfaces.

- The steps for achieving at least one limiting volume and for limiting the tool path to the volume defined by the intersection of the at least one limiting volume and the delta volume.

- The steps to obtain a solid model of at least one avoidance volume and not allow the toolpath to enter it.

The following characteristic features are important for the process of modeling subsequent machining operations that are carried out on a semi-finished part to produce a workpiece:

(1) Creating a volume model of the semi-finished part;

(2) Creating a solid model of the workpiece;

(3) performing a first logical operation to subtract the workpiece model from the semi-finished product model to obtain an initial delta volume;

(4) Creating a machining strategy;

(5) using the initial delta volume and the machining strategy to calculate an initial tool path for at least one machining tool;

(6) Determining an initial machining volume from the initial tool path;

(7) performing a second logical operation to subtract the initial processing volume from the initial delta volume to obtain the next delta volume;

(8) repeating step (5) with the next delta volume to obtain the next tool path, step (6) to determine a next machining volume from the next tool path, and step (7) to obtain yet another delta volume, and

(9) Repeat step (8) until all delta volumes have been processed.

- The step of sequentially applying the initial toolpath and each subsequent toolpath to control a machining tool to remove the initial delta volume and each subsequent delta volume from the stock part.

- The solid model of the workpiece is obtained by retrieving data stored in a data storage device.

- The solid model of the semi-finished part is achieved by retrieving data stored in a data storage device.

- The machining strategy is achieved by retrieving data stored in a data storage device.

- The processing strategy is achieved by applying an expert system.

- The machining strategy is achieved by data entered by a user.

- The step of performing the additional logical operations to subtract the initial machining volume and each next machining volume from the stock model to obtain an initial modified stock model and the next modified stock model, thereby obtaining a solid model of the remaining stock part after the initial and each next traversal of the machining tool according to the respective initial and each next tool path.

- The manufacturing attributes for the initial delta volume are obtained by retrieving manufacturing data stored in a data storage device, the manufacturing attributes including data used in step (5) to determine the initial tool path and in step (8) to determine the next tool path.

- The manufacturing strategy contains the manufacturing attributes.

- The initial delta volume further includes a plurality of sub-delta volumes, wherein steps (5) to (9) are applied sequentially to each of the sub-delta volumes.

- The majority of sub-delta volumes are obtained from the initial delta volume by applying an expert system.

- The sequence in which steps (5) to (9) are applied to the sub-delta volumes is determined by application of an expert system.

- The manufacturing attributes are obtained for the initial delta volume by applying an expert system, the manufacturing attributes containing data used in step (5) in determining the initial tool path and in step (8) in determining the next tool path.

- The step of sequentially applying the initial toolpath and each next toolpath to control at least one machining tool for removing the delta volume and each next delta volume from the semi-finished part, wherein the manufacturing attributes further include data used in selecting the at least one machining tool.

- The machining strategy contains the machining attributes.

In connection with a method for modelling successive machining operations carried out on a semi-finished part to produce a workpiece, the following features are essential:

(1) Creating a volume model of the semi-finished part;

(2) Creating a solid model of the workpiece;

(3) Creating a processing strategy;

(4) Applying the machining strategy to calculate an initial tool path through the model of the semi-finished product while avoiding the model of the workpiece;

(5) Determining an initial machining volume from the initial tool path;

(6) performing a logical operation to subtract the initial machining volume from the model of the semi-finished product to obtain a next model of the semi-finished product;

(7) repeating step (4) using the next model of the semi-finished product to obtain a next semi-finished product path, step (5) to determine a next machining volume from the next tool path, and step (6) to obtain yet another next model of the semi-finished product by using the next machining volume; and

(8) Repeat step (7) until the next model of the semi-finished product is smaller than a predetermined volume.

- The step of successively applying the initial toolpath and each subsequent toolpath to control a machining tool.

- The solid model for the semi-finished part is achieved by retrieving data stored in a data storage device.

- The solid model for the workpiece is obtained by retrieving data stored in a data storage device.

- Step (4) is performed by classifying the model of the workpiece as an avoidance volume by applying an expert system.

- Step (4) further contains the sub-steps:

(i) arranging the model of the workpiece in the model of the semi-finished product;

(ii) achieving the initial flat cross-section at an initial depth of the model of the semi-finished part and the model of the workpiece arranged therein;

(iii) performing a two-dimensional logical operation to subtract the initial cross-section of the model of the workpiece from the initial cross-section of the model of the semi-finished part to obtain an initial cross-section of the semi-finished part to be removed; and

(iv) Using the initial cross-section of the stock part to be removed to calculate an initial tool path for a machining tool.

- as well as the steps

(1) Creating a two-dimensional avoidance profile; and

(2) Performing a two-dimensional logical operation to subtract the avoidance profile from the cross-section of the semi-finished part to be removed before executing substep (iv).

In a method for modeling successive machining operations that are carried out on a semi-finished part to produce a workpiece, the following steps are characteristic:

(1) Creating a machining strategy;

(2) Creating a volume model of the semi-finished part;

(3) Creating a solid model of the workpiece;

(4) Creating a two-dimensional profile of an avoidance volume;

(5) arranging the model of the workpiece within the model of the semi-finished product;

(6) Creating a flat initial cross-section at an initial depth of the model of the semi-finished part and the model of the workpiece arranged therein;

(7) performing a first two-dimensional logical operation to subtract the initial cross-section of the model of the workpiece from the initial cross-section of the model of the semi-finished part to obtain a cross-section of the semi-finished part to be removed;

(8) performing a second two-dimensional logical operation to subtract the profile of the avoidance volume from the cross-section of the semi-finished part to be removed;

(9) Applying the machining strategy and the initial cross-section of the semi-finished part to be cut off to calculate an initial tool path for a machining tool;

(10) determining an initial machining volume from the initial tool path at the initial depth;

(11) Not allowing the tool path to enter the cross-section of the workpiece model or the avoidance profile;

(12) repeating steps (7) to (11) using the next planar cross sections of the model of the workpiece and the model of the semi-finished product obtained at a next depth; and

(13) Repeating step (12) until the semi-finished part to be removed is less than a predetermined volume.

- The machining strategy is achieved by retrieving data from a data storage device.

- The processing strategy is achieved by applying an expert system.

- The machining strategy is achieved from data entered by a user.

- The solid model of the semi-finished part is obtained by retrieving data stored in a data storage device.

- The solid model of the workpiece is obtained by retrieving data stored in a data storage device.

- The two-dimensional profile of an avoidance volume is obtained by retrieving data stored in a data storage device.

- The two-dimensional profile of an avoidance volume is obtained by applying an expert system.

For a device for modeling successive machining operations performed on a semi-finished part to produce a workpiece, the following features are most important:

(1) means for obtaining a feature volume to be removed from the semi-finished part to produce the workpiece;

(2) means for determining an initial tool path for at least one machining tool from the feature volume;

(3) means for determining an initial machining volume from the initial tool path;

(4) means for performing a first logical operation to subtract the initial processing volume from the feature volume to obtain a delta volume;

(5) means for determining the next tool path from the delta volume;

(6) means for determining a next machining volume from the next tool path; and

(7) means for performing a second logical operation to subtract each next processing volume from the delta volume to obtain a next delta volume.

- Means for sequentially applying the initial toolpath and each subsequent toolpath to control a machining tool to remove the delta volume and each subsequent delta volume from the stock part.

- A data storage device and a means for retrieving the feature data stored in the data storage device.

- Means for obtaining the manufacturing attributes for the feature volume by retrieving the manufacturing data stored in the data storage device.

- Means for sequentially applying the initial tool path and each next tool path to control the at least one machining tool for removing the delta volume and each next delta volume from the semi-finished part, and means for selecting the at least one machining tool based on the manufacturing attributes.

- A dividing device for dividing the feature volume into a plurality of sub-feature volumes.

- Means for sequentially applying the initial toolpath and each next toolpath to control a machining tool to remove the delta volume and each next delta volume from the stock part for each of the plurality of sub-feature volumes.

- The means for determining an initial tool path for at least one machining tool from the feature volume with means for achieving and applying a machining strategy.

Claims (35)

1. Method for producing a workpiece (201) with the steps: [1] Creating a computer model of the workpiece (201) using a solid modeler; [2] Creating a computer model of a semi-finished part (301) using a solid modeler; [3] Drawing up a schedule for manufacturing the workpiece (201); [4] Linking the manufacturing attributes to the model of the workpiece (201); [5] Determining at least one delta volume (501, 502, 503) to be removed from the semi-finished part (301) by subtracting the model of the workpiece (201) from the model of the semi-finished part (301), and recording the manufacturing attributes from the model of the workpiece (201) to a corresponding area of the at least one delta volume (501, 502, 503); [6] Creating a model of a manufacturing setting; [7] Creating a machining strategy; [8] Calculating tool paths for a numerically controlled manufacturing facility from the at least one delta volume (501, 502, 503) according to the machining strategy and the model of the manufacturing setting; [9] Calculating at least one machining volume (601) which represents the total volume of the space to be removed by the cutting tool; [10] Subtracting the at least one processing volume (601) from the at least one delta volume (501, 502, 503) to obtain a new delta volume; [11] Subtracting the at least one processing volume (601) from the model of the semi-finished part (301) in order to thereby modelling the machining of the tool path and verifying that the tool paths have not damaged the workpiece (201); [12] Repeating steps [7] to [11] until the removal of the at least one delta volume (501, 502, 503) has been modelled; and [13] Manufacturing the workpiece (201) according to the flow chart by transferring the tool paths to the numerically controlled machining tool, whereby steps [1] to [7] can generally be carried out in any order, provided that step [1] must precede step [4], steps [1] and [2] must precede step [5], and steps [11] to [7] must precede step [8]. 2. The method of claim 1, wherein the model of the manufacturing setting is obtained by retrieving data stored in a data storage device or by using an expert system or data entered by a user. 3. Method for modeling successive machining operations carried out on a semi-finished part (301) to produce a workpiece (201), comprising: [1] Creating at least one feature volume (501, 502, 503) which is to be removed from the semi-finished part (301) to produce the workpiece (201); [2] Creating a machining strategy; [3] determining an initial tool path for at least one machining tool from the at least one feature volume (501, 502, 503) and the machining strategy; [4] Determining an initial machining volume (601) from the initial tool path; [5] performing a logical operation to subtract the initial processing volume (601) from the feature volume (501, 502, 503) to obtain the delta volume; [6] repeating step [3] with the delta volume to obtain a next tool path, step [4] to determine a next machining volume from the next tool path and step [5] to obtain a next delta volume; and [7] Repeat step [6] until all delta volumes have been processed. 4. The method of claim 3, further comprising the step of sequentially applying the initial tool path and each subsequent tool path to control the machining tool to remove the delta volume and each subsequent delta volume from the semi-finished part. 5. The method of claim 3 or 4, wherein the feature volume (501, 502, 503) is obtained by retrieving feature data stored in a data storage device or by applying an expert system. 6. Method according to one of claims 3 to 5 with the further step of determining an optimal feed rate in the initial and each subsequent tool path, wherein preferably the optimal feed rate in the initial and each subsequent tool path is continuously variable. 7. The method of any one of claims 3 to 6, wherein the manufacturing attributes for the feature volume (501, 502, 503) are obtained by retrieving manufacturing data stored in a data storage device, and wherein the manufacturing attributes include data used in step [3] to determine the initial tool path and in step [6] to determine the next tool path, wherein the machining strategy preferably includes the manufacturing attributes. 8. The method of any one of claims 3 to 7, wherein the feature volume (501, 502, 503) further includes a plurality of sub-feature volumes and wherein steps [3] to [7] are applied sequentially to each of the sub-feature volumes, wherein the plurality of sub-feature volumes are preferably obtained from the feature volume by application of an expert system. 9. The method of claim 8, further comprising the step of sequentially applying the initial tool path and each next tool path to control a machining tool to remove the delta volume and each next delta volume from a stock part (301) for each of the plurality of sub-feature volumes. 10. The method according to claim 9, wherein the sequence in which the sub-feature volumes are removed from the semi-finished part (301) is determined by applying an expert system. 11. The method of claim 9 or 10, wherein the plurality of sub-feature volumes each depend on one of the plurality of desired planar surfaces of the workpiece (201) to be manufactured, the surfaces being in parallel planes, and further comprising the step of removing these sub-feature volumes in a sequence determined by their relative clearance in a direction perpendicular to these planar surfaces. 12. Method according to one of claims 3 to 11 with the further steps of achieving at least one boundary volume and limiting the tool path to the volume which is defined by the intersection of at least one boundary volume and the delta volume. 13. Method according to one of claims 3 to 12 with the further steps of obtaining a volume model of the at least one avoidance volume and preventing the tool path from entering it. 14. Method according to claims 3 or 4, wherein the feature volume (501, 502, 503) is obtained by the steps : [1] Creating a volume model of a semi-finished part (301); [2] Creating a solid model of a workpiece (201); [3] performing a first logical operation to subtract the workpiece model from the semi-finished product model to obtain the feature volume (501, 502, 503) as an initial delta volume; and wherein the workpiece (201) is produced by the further steps : [4] Creating a machining strategy; [5] Using the initial delta volume and the machining strategy to calculate the initial tool path for at least one machining tool; [6] Determining an initial machining volume (601) from the initial tool path; [7] performing a second logical operation to subtract the initial processing volume (601) from the initial delta volume to obtain a next delta volume; [8] Repeat step [5] with the next delta volume to obtain a next tool path, step [6] for determining a next machining volume from the next tool path and step [7] for obtaining a next delta volume, and [9] Repeat step [8] until all delta volumes have been processed. 15. The method of claim 14, further comprising the steps of sequentially applying the initial tool path and each subsequent tool path to control a machining tool to remove the initial delta volume and each subsequent delta volume from the semi-finished part (301). 16. The method according to claim 14 or 15, wherein the volume model of the workpiece (201) and/or the semi-finished part (301) is obtained by retrieving data stored in a data storage device. 17. A method according to any one of claims 14 to 16, comprising the further step of performing additional logical operations to subtract the initial machining volume and each subsequent machining volume from the stock model to obtain a modified initial stock model and modified subsequent stock models, thereby obtaining a solid model of the remaining portion of the stock after the initial and subsequent traversal of the machining tool through the respective initial and subsequent tool paths. 18. The method of any one of claims 14 to 17, wherein the initial delta volume further includes a plurality of sub-delta volumes, and wherein steps [5] to [9] are applied sequentially for each of the sub-delta volumes, wherein the plurality of sub- Delta volume is preferably obtained from the initial delta volume by applying an expert system. 19. The method of claim 18, wherein the sequence in which steps [5] to [9] are applied to the sub-delta volumes is determined by applying an expert system. 20. Method according to one of claims 14 to 19, wherein manufacturing attributes for the initial delta volume are obtained by applying an expert system, and wherein the manufacturing attributes include data used in step [5] for determining the initial tool path and in step [8] for determining the next tool path, wherein the manufacturing strategy preferably includes the manufacturing attributes. 21. Method according to one of claims 7 to 20 with the further step of sequentially applying the initial tool path and each next tool path to control at least one machining tool for removing the delta volume and each next delta volume from the semi-finished part (301), and wherein the manufacturing attributes further contain data used in the selection of the at least one machining tool, and preferably the further step of controlling the at least one machining tool with an optimal feed rate corresponding to the initial and each next tool path, wherein the optimal feed rate corresponding to the initial and each next tool path is preferably continuously variable. 22. The method according to claim 21, wherein the tool path determined from the manufacturing attributes further comprises specification data for machining tool entry modes and exit directions, type of cutting shape, maximum cutting depth and coolant control. 23. Method for modeling successive machining operations to be carried out on a semi-finished part (301) to produce a workpiece (201), comprising: [1] Creating a volume model of a semi-finished part (301); [2] Creating a solid model of a workpiece (201); [3] Creating a machining strategy; [4] Using the machining strategy to calculate an initial tool path through the model of the semi-finished product (301) while avoiding the model of the workpiece (201); [5] Determining an initial machining volume (601) from the initial tool path; [6] performing a logical operation to subtract the initial machining volume (601) from the model of the semi-finished product (301) to obtain a next model of the semi-finished product; [7] Repeating step [4] using the next model of the semi-finished product to obtain a next tool path, step [5] to determine a next machining volume from the next tool path and step [6] to obtain yet another next model of the semi-finished product using the next machining volume; and [8] Repeat step [7] until the next model of the semi-finished product is less than a predetermined volume. 24. A method according to claim 23, comprising the further step of successively applying the initial toolpath and each subsequent toolpath to control a machining tool. 25. The method of claim 23 or 24, wherein step [4] is performed by classifying the model of the workpiece as an avoidance volume through the application of an expert system. 26. The method according to any one of claims 23 to 25, wherein step [4] further comprises the substeps: [i] arranging the model of the workpiece (201) in the model of the semi-finished product (301); [ii] achieving a flat initial cross-section at an initial depth of the model of the semi-finished part (301) and the model of the workpiece arranged therein (201); [iii] performing a two-dimensional logical operation to subtract the initial cross-section of the model of the workpiece (201) from the initial cross-section of the model of the semi-finished part (301) to obtain an initial cross-section of the semi-finished part to be removed; and [iv] Using the initial cross-section of the semi-finished part to be removed to calculate an initial tool path for a machining tool. 27. Method according to claim 26 with the further steps [1] Creating a two-dimensional avoidance profile; and [2] Performing a two-dimensional logical operation to subtract the avoidance profile from the cross-section of the semi-finished part to be removed before executing sub-step [iv]. 28. Method for modelling successive machining operations performed on a semi-finished part (301) to produce a workpiece (201), comprising: [1] Creating a machining strategy; [2] Creating a volume model of the semi-finished part (301); [3] Creating a solid model of the workpiece (201); [4] Creating a two-dimensional profile of an avoidance volume; [5] Arranging the model of the workpiece (201) in the model of the semi-finished product (301); [6] Creating a flat initial cross-section in an initial depth of the model of the semi-finished part (301) and the model of the workpiece arranged therein (201); [7] performing a first two-dimensional logical operation to subtract the initial cross-section of the model of the workpiece (201) from the initial cross-section of the model of the semi-finished part (301) to obtain a cross-section of the semi-finished part to be removed; [8] Performing a second two-dimensional logical operation to subtract the profile of the avoidance volume from the cross-section of the semi-finished part to be removed; [9] Using the machining strategy and the initial cross-section of the semi-finished part to be removed to calculate an initial tool path for a machining tool; [10] Determining an initial machining volume (601) from the initial tool path at the initial depth; [11] Preventing the tool path from entering the cross-section of the model of the workpiece or the avoidance profile; [12] Repeat steps [7] to [11] using the next planar cross-section of the model of the workpiece and the model of the semi-finished part obtained at a next depth; and [13] Repeat step [12] until the semi-finished part to be removed is less than a predetermined volume. 29. Method according to one of claims 23 to 28, wherein the volume model of the semi-finished part (301) and/or the workpiece (201) is obtained by retrieving data stored in a data storage device. 30. A method according to claim 28 or 29, wherein the two-dimensional profile of an avoidance volume is obtained by retrieving data stored in a data storage device or by applying an expert system. 31. A method according to any one of claims 1 to 30, wherein the processing strategy is achieved by retrieving data from a data storage device or by applying an expert system or by inputting data by a user. 32. Device for modeling successive machining operations to be carried out on a semi-finished part (301) to produce a workpiece (201), with: [1] a device for achieving a feature volume (501, 502, 503) which is to be removed from the semi-finished part (301) to produce the workpiece (201); [2] means for determining the initial tool path for at least one machining tool from the feature volume (501, 502, 503); [3] means for determining an initial machining volume (601) from the initial tool path; [4] means for performing a first logical operation to subtract the initial processing volume (601) from the feature volume (501, 502, 503) to obtain a delta volume; [5] means for determining a next tool path from the delta volume; [6] a device for determining a next machining volume from the next tool path; and [7] means for performing a second logical operation for subtracting each next machining volume from the delta volume to obtain a next delta volume, wherein the means for determining an initial tool path for at least one machining tool from the feature volume preferably comprises means for obtaining and applying a machining strategy. 33. Apparatus according to claim 32 with a further device for sequentially applying the initial tool path and each next tool path for controlling a machining tool for removing the delta volume and each next delta volume from the semi-finished part (301), preferably wherein a data storage device and/or a device for retrieving feature data stored in the data storage device are provided. 34. Apparatus according to claim 33, comprising further means for obtaining manufacturing attributes for the feature volume (501, 502, 503) by retrieving manufacturing data stored in the data storage means, wherein the means for successively applying the initial tool path and each next tool path are preferably provided to control at least one machining tool for removing the delta volume and each next delta volume from the semi-finished part (301), and means for selecting the at least one machining tool based on the manufacturing attributes. 35. Apparatus according to claim 33 or 34, further comprising dividing means for dividing the feature volume (501, 502, 503) into a plurality of sub-feature volumes, and further comprising means for sequentially applying the initial tool path and each next tool path to control a machining tool for removing the delta volume and each next delta volume from the stock part (301) for each of the plurality of sub-feature volumes.